The objective is to understand how genes control metabolism in eucaryotes, in particular, how they control enzyme synthesis. I have chosen a group of enzymes in Neurospora which I call the 'phosphorus family'. All of them serve to harvest phosphorus from the medium when it is in short supply, and all are repressed when phosphorus is plentiful. The four known regulatory genes work in a hierarchy to control the structural genes. The regulatory gene exercising immediate command is nuc-1; the product of this gene is needed to turn on expression of the unlinked structural genes. A major aim is to isolate the nuc-1 gene product and study the mechanism of its control of structural genes. In particular, I would like to study how it is bound to control sites, how alteration of those sites alters control by nuc-1 product, and how nuc-1 product is, in turn, affected by other regulatory gene products. My colleagues and I are attempting to clone the structural gene for alkaline phosphatase and other members of the family, plus any adjacent control site(s) into E. coli plasmids. I hope to use the DNA to enrich for nuc-1 product so that it can be isolated in quantity. In addition, we will study proteins that bind to untranscribed regions next to the ribosomal DNA genes. I plan to test the hypothesis that rRNA synthesis may be under repression control by the nuc-1 product and by regulators of sulfur, nitrogen, and carbon metabolism.